The present invention relates generally to operations performed and equipment utilized in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides an electrically operated deep set safety valve.
It is sometimes desirable to set a safety valve relatively deep in a well. For example, a safety valve may be set at a depth of 10,000 ft or more. However, operating a safety valve at such depths present a variety of problems which tend to be expensive to overcome. Most offshore hydrocarbon producing wells are required by law to include a surface controlled subsurface safety valve (SCSSV) located downhole in the production string to shut off the flow of hydrocarbons in an emergency. These SCSSV's are usually set below the mudline in offshore wells. Since offshore wells are being drilled at ever increasing water depths and in environmentally sensitive waters, it has become very desirable to electrically control these safety valves to eliminate the use of hydraulic fluids and be able to set the safety valves at virtually unlimited water depths. However, because of the depth, it is difficult to deliver the electric power to operate these valves. One or more wires can be run down the well to the valves, although the number is limited by space and design considerations. Moreover, a number of downhole tools, instruments, etc. compete for the limited amount of power available through the lines.
In addition, once a valve or other device is installed downhole it is difficult to remove and replace. Should it be desired to add or modify the functionality of the downhole components, it is difficult and expensive to effect the desired change.
Moreover, in a well environment, typical pressures, temperatures, salinity, pH levels, vibration levels, etc., downhole vary and are demanding. Moreover, the environment is often corrosive, including chemicals dissolved in, or otherwise carried by, the hydrocarbons or injected chemicals, such as hydrogen sulfide, carbon dioxide, etc. Thus, downhole components must be designed to withstand these conditions or isolated from the environment, such as by a sealed chamber.